on-double-click

Arguments:
dialog-item

Returns the value of the on-double-click event property of
dialog-item. The value of the on-double-click property should be
a function object or a function name (a symbol naming a
function). This function is called when the left mouse button is
double-clicked while the mouse cursor is over
dialog-item. This function should accept two
arguments, the dialog holding dialog-item and dialog-item itself. The
value may be nil if no function need be run.

The value may also be the special keyword
:push-again. This value causes the second click of
a double-click to call the on-change function of the control,
if any. Since the first click of a double-click always calls
the on-change
function (if any), this special value means that every click of a
rapid series of clicks will call the on-change function. By contrast,
when on-double-click is nil, nothing is done on the second click of a
double-click. This default behavior prevents the user from
accidentally calling the on-change function twice on an
accidental double-click, and so :push-again must be
specified explicitly when rapid-fire clicking to invoke the on-change function for
every click is desired instead. (A small limitation of
:push-again is that the control will not visibly
depress a second time for the second click of a double-click, despite
the name.)

Consider a use of on-change to change the value
displayed in a static text widget. If only two values are possible,
suppressing an immediate second click (as is done when on-double-click is
nil) may be useful as the second click is
probably unintended. But if on-change cycles through a longer
list of values, rapid multiple clicks are likely intentional and the
:push-again for on-double-click would be
appropriate.

See cg-events.htm for information about
event handling in Common Graphics.

Copyright (c) 1998-2012, Franz Inc. Oakland, CA., USA. All rights reserved.Documentation for Allegro CL version 8.2. This page was not revised from the 8.1 page.Created 2010.1.21.